...a glacier out in the ocean. However, once you pour in a hot beverage, the massive ice formation slowly melts down into nothingness.
A great tool for picking up office babes around the water cooler (tell them the plight of the polar bear makes you cry).
The cup is a companion piece to this "global warming mug", which
...looks like a regular mug with a map of our planet drawn on it. Blue water, green land… and some chemical formulas.
The chemical formulas, which are presumably not coffee soluble, cause the map to change to reflect rising sea-levels brought about by AGW. A great Xmas gift that allows you to lay an endless guilt trip on skeptical friends.
PS. A "glacier out in the ocean"?